As an alternative to performing more invasive medical procedures, many physicians are utilizing endoscopes and catheters to perform diagnostic and therapeutic procedures on the internal tissues of patients. With this less invasive approach, a medical instrument, such as an endoscope or a catheter is advanced to a site of interest in order to perform the indicated procedure. Most endoscopes and catheters have a flexible shaft that allows the endoscope or catheter to wind its way through bends in the patient's anatomy until it reaches the tissue of interest. In order to advance the flexible shaft, most steerable endoscopes have a system of control cables that act in pairs to help direct the distal tip of the shaft. Each control cable is disposed opposite to its pair, and the control cables move in opposition to one another such that as one control cable is being pulled, the other is being released. The effect is to bend the tip of the shaft in a desired direction. In many endoscopes or catheters, the control cables have an outer sheath and an inner core wire. The outer sheath acts to transmit the longitudinal motion of the core wire to the distal tip of the endoscope. During a medical procedure, it is not uncommon for the shaft to form one or more loops as it is navigated to the tissue of interest. When a shaft including a control cable is looped, the outer sheath becomes increasingly stiff and harder to navigate within the body. At every bend of the shaft, the distances traveled by the core wire and its respective outer sheath differ, producing tension in the outer sheath and/or the core wire and increasing the amount of force needed to exert longitudinal force in the pull wire. This results in the user having less control over the tip of the device and less ability to detect external forces acting on the tip. Therefore, there is a need for a navigation system for use in steerable medical instruments that is still steerable at low forces if looped in the body.